Atlanta opening independent probe into massive fish kill in Chattahoochee River

Thousands of fish were killed over a 20-mile stretch of the Chattahoochee River. \ CBS

The City of Atlanta has asked an outside firm to do an independent investigation into the deaths of thousands of fish in the Chattahoochee River in May.

In a statement, the city’s Department of Watershed Management said it has retained engineering and consulting firm Brown and Caldwell “to conduct an independent evaluation of system operations at the West Area CSO Tunnel Treatment Facility and the associated tunnel operations.”

Officials say the massive storm on May 20 dumped three inches of rain in an hour, leading to stormwater runoff from the city’s sewage system into the river. The runoff and high temperatures caused fish to suffocate, killing thousands of fish over a 20-mile stretch.

Jason Ulseth, the executive director of the Chattahoochee Riverkeeper, told CBS News Atlanta at the time that he had never seen anything like it in his more than 20 years at the organization.

While the Department of Watershed Management is conducting its own investigation into the causes of the runoff and deaths, it says the firm’s evaluation will offer recommendations on how the city can strengthen its operations.

“The review will assess rainfall conditions, system performance during the event, and the source of reported sludge residue, as well as determine whether observed conditions are directly related to the storm or other contributing factors,” the DWM’s statement read, in part.

Both investigations are in collaboration with the Georgia Environmental Protection Division.